This invention relates, in general, to semiconductors, and more particularly, to optical semiconductor components.
Conventionally micromachined accelerometers have a movable seismic mass that typically serves as an electrode for a motion sensing capacitor. The movable seismic mass is deflected toward or away from a stationary electrode in response to an acceleration. The measured capacitance between the seismic mass and the stationary electrode is dependent upon numerous factors including the distance between the seismic mass and the stationary electrode. Accordingly, in order to use the measured capacitance to accurately determine acceleration, the seismic mass should be planar so that a perpendicular distance between a portion of the seismic mass and a portion of the stationary electrode is the same as another perpendicular distance between another portion of the seismic mass and another portion the stationary electrode. However, a planar seismic mass is difficult to manufacture because of the topography underlying the seismic mass and also because of the internal mechanical stress of the seismic mass.
The sensitivity of the conventional micromachined accelerometer is also dependent upon the area of the seismic mass that overlaps the stationary electrode and is further dependent upon the magnitude of the measured capacitance. A larger measured capacitance can be used to increase the sensitivity of the conventional accelerometer, but a larger measured capacitance also increases the probability of electrical latching between the stationary electrode and the seismic mass wherein the electrical latching damages the accelerometer.
Therefore, a need exists for an improved micromachined accelerometer. The accelerometer should not be too sensitive to the planarity of a seismic mass and should not suffer from electrical latching.